Two major areas of experimentation in oral biology are proposed, both of which relate to membrane receptor function and associated events. The first is concerned with biochemical aspects of preneural taste perception. Experiments, based on the application of reversible and irreversible probes, are designed to delineate the molecular events involved in the transduction of the response from the membrane receptor to the innervating nerve. Irreversible inhibitors, including protein modification reagents and receptor affinity labels, will be applied to rat gustatory tissue in situ, where the effects can be judged in the context of electrophysiological function. The location of the inactivation site and specificity relative to events uniquely associated with the response elicited by different stimuli will be judged by kinetic analysis of the rates of decay of summated electro-physiological activity. The application of reversible probes with a strong affinity for bitter-type receptors will be explored to determine if cell-surface receptor topography can be visualized by microautoradiography. Furthermore, electrophysiological experiments are proposed to evaluate the extent of cooperativity of the response from sodium stimulation and applicability of an allosteric model. The second section outlines an experimental approach to the characteristic of glycosyltransferases and cell surface dextran receptors from the cariogenic bacteria, S. mutans. Extracellular dextransucrase will be isolated by affinity chromotography and characterized bio-physically and kinetically. The results will be applied to design of active site affinity labels to further explore the mechanism of action. Dextran binding proteins which are partly responsible for S. mutans adherence to polysaccharides in dental plaque will be isolated and characterized using fluorescent-dextran derivatives. The fluorescent probes will also be exploited in the characterization of the dextran (acceptor) site on dextransucrase.